Labyrinth seals



F. W.y W. MORLEY ETAL `LABYRINTH SEALS 2 Sheets-Sheet 2 FIC-5.5.

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AT TORN EYS March 19, 1963 Filed Jan. 19, 1959 F I G. 4

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United States Patent O 3,082,010 LABYRINTH SEALS Frederick William Walton Morley, Castle Donington, Wilfred Henry Wilkinson, Tumditch, and Charles Samuel Broad, En'teld, England, assignors to Rolls- Royce Limited, Derby, England, and Delaney Gallay Limited, London, England, both British companies Filed Jan. 19, 1959, Ser. No. 787,607 Claims priority, application Great Britain Jan. 20, 1958 9 Claims. (Cl. 277--16) This invention is for improvements in labyrinth seals of the type which -are used to prevent leakage of a iluid between a rotating member and an adjacent stationary member.

Such seals frequently consist yof a series of annular tins or projections carried by one or both the members the edges of which are in close proximity to the other member or to like fins or one or more projections on the other member.

According to this invention the sealing member is built up of a plurality Iof metal annuli initially separate or in spiral form, mounted together las a stack of separate annuli or spiral convolutions on one of the members and axially spaced apart at their peripheral edges by means of av separate spacer piece or pieces located between adjacent annuli or convolutions.

Preferably the annuli are carried by the stator only and co-operate with one or more annular projections on the rotating member, `and are of softer metal or one having a lower melting point than these latter projections so that if rubbing occurs it will be these metal annuli which will be worn away.

Thus a tip shroud of a turbine blade of an internal combustion turbine engine may carry one or more annular projections each cooperating with a stack of annuli carried'by the surrounding structure to form a gas seal between the tip platform and the surrounding structure.

If the annuli are united in a continuous spiral the spacer can also be in the form of a continuous spiral.

Alternatively if separate annuli are used the separate spacer pieces can each comprise an annulus of thin metal ICC means constructed in -accordance with the present invention; Y

FIGURE 2 is a section to a larger scale of one construction of the sealing means,

FIGURE 3 is a developed view` in the direction of arrow '3 on FIGURE 2;

FIGURE 4 is `a part section, again to a larger scale, of a modification of the construction illustrated in FIG- URE 2;

FIGURE 5 is a developed view in the direction of arrow 5 on FIGURE 4;

FIGURE 6 -is a View corresponding to FIGURE 4 of another modification of the construction illustrated in FIGURE 2;

' FIGURE 7 is a developed view in the direction of arrow 7 on FIGURE 6; `and FIGURE 8 is a part section through a turbine stator assembly to the same scale as FIGURE l.

In FIGURE 1 is shown part of `a turbine rotor of a gas turbine engine, the rotor comprising a row of rotor blades 10, each blade being provided with a shroud portion 10a at its radially outer end, said shroud portions 10a each and each abut portions of separate sealing annuli, remote from the sealing portions.

The separate spacer pieces can each comprise an annulus of thin metal provided with a plurality of part spherical dimples.

Alternatively the annulus of this metal is provided with a number of flat sided corrugations.

In a further yalternative arrangement the annulus of thin metal` can be provided with a number of corrugations of sinusoidal yform.

Preferably the cor-rugations extend in a radial direction. The annuli and separate spacer means may be secured together by mechanical means or by brazing, Welding, -resin bonding or the like. The metal from which the annuli are formed is preferably of due order of 2 to 6 thousandths of `an inch in thickness, but `for some applications Where high temperatures and/or pressures are experienced a thicker metal may be found desirable.

A method of making the annuli comprises forming a continuous strip to the desired cross-section by extruding, drawing or rolling the strip, winding the 'formed strip continuously round a mandrel so that the wider surfaces of the strip lie in substantially radial planes to `form a spiral of annuli. If separate annuli are employed the wound strip is cut axially of the mandrel so 1as to form the desired plurality of separate annuli.

Some embodiments of this invention will now be described with reference to the `accompanying drawings in which:

FIGURE l is a section through part of a turbine rotor assembly of a Igas turbine engine, incorporating sealing having a pair of axially-spaced outwardly-directed circumferentially-extending ribs 10b.

Each of the ribs 10b co-operates with `one of a pair of axially-spaced sealing members 11 secured to a ring 12 which surrounds the shroud portions 10a of the rotor blades 10 and is spaced radially therefrom.

The ring 12 is of substantially frusto-conical -form and is provided at each end with an axially-extending portion 12a having an inwardly facing annular recess 12b in which is received the sealing means 11, said sealing means 11 being retained against axial movement by retaining ring 13 tted in and welded to the axially-extending portion 12d.V

Ring 12 is secured to the surrounding stator structure,

indicated generally at 14, by having the left-hand axiallyextending portion 12a received in an open-ended axiallyfacing channel 15 formed in the stator structure 14 and by having the right-hand axially-extending portion 12a tackwelded along its edge to the stator structure 14.

' A circumferentially-extending chamber 16, formed between the ring 12 and the stator structure 14, is supplied with va flow of cooling air through a series of drilled passages 17 provided in the stator structure 14, said cooling air flowing out of the chamber 16 through a further series of drilled passages 18.

One -form in which the sealing means 11 may be constructed is shown in FIGURES 2 and 3 and comprises a stack of thin metallic annuli 19 each of which has an axially-thin sealing portion 19b. Each annulus 19 is formed lfrom thin metal strip of say,

6 l m thickness The annuli 19 are each provided with an axially-directed 4ilange 20 at -their outer periphery, and adjacent annuli 19 are spaced axially apart by separate spacer means 21. Each separate -spacer 21 comprises an annulus of thin metal which is provided with a plurality of part spherical depressions or dimples 22, and each -spacer 21 is secured to adjacent annuli 19 by means of spot welds providedA in the troughs of Ia number of the part spherical depressions or dimples 22. Each spacer 21 is of a less radial depth than the annuli 19 so as to leave the sealing portions 19b clear of the spacers 21.

Each annulus 19` is secured to a ring 23 by having its axially directed flange 20 welded or brazed thereto and the assembly of annuli119 and spacer means 21 is clamped between two L-section rings 24 and 25 Which are secured to the ring 23.

FIGURES 4 and 5 show a modification of the construction just described with reference to FIGURES 2 and 3. In this modiiied construction the annuli of thin metal which `form the separate spacer means 21 are each provided with a number of radially-extending at sided corrugations 26, seen more clearly in FIGURE 5. The hat side of each corrugation 26 being welding to the annulus 19 against which it abuts.

A further modification of the spacer means 21 is illustrated in FIGURES 6 and 7. The separate spacer means 21 are each provided with a number of radiallyextending corrugations 27 which are of sinusoidal form and are -sucured to adjacent annuli 19 by a weld provided in the trough of each cormgation.

T'ihe ring 23 and the two end rings 24 and 25 may form the main structural parts of a presfabricated sheet metal ring structure illustrated in FIG. 8.

The pre-fabricated sheet metal structure is retained in the stator structure 14 in a manner similar to that of ring 12 and as described With reference to lFIGURE 1.

By having the sealing means 11 constructed of thin metal strips of the order of 6l l m thickness the clearance between the sealing portion -19b and the rotatable ribs 10b of the shroud portion l10n is not so critical as with previously known types of seals.. If the ribs 10b come into rubbing contact with the sealing portions 19b during operation, part of the sealingportions 19!) will melt due to the heat set up by friction and the ribs 10b ywill therefore cut their own path vin the sealing portions 19h.

It will be appreciated that if the two parts of the sealing means 11 do rub together no damage will be done to the ribs 10b. If the annuli 19 become damaged to a degree which entails their replacement, then the tack'- weld-s securing the ring 12 to the stator structure 1 4 can be machined away and the ring 12 may then be withdrawn from the stator structure 14 so that the damaged stack of annuli 19 can be replaced by a new stack.

In each of the arrangements described the separate annuli could be replaced by a continuous strip of spiral form so that the sealing member is lbuilt up of continuous convolutions separated by a continuous, spiral spacer piece.

We claiml:

1. In apparatus comprising a rotor member and a stator member, in combination; a labyrinth seal and a confronting rib one within the other, said seal being carried by one of said members and comprising a stack lof thin strip metal annuli having circular peripheral edges, a plurality of distance pieces formed separately from and interleaved with said annuli to space the latter axially apart and strengthen them, said distancepieces being of less radial depth than said annuli to leave said peripheral sealing edges clear, and at least one relatively sharp continuous rib cmried by the other of said members and arranged in substantial sea-ling relation-ship with said annuli, said rib being sized to cut its own path in the annuli if rubbing therebetween occurs.

2. A seal as claimed in claim 1 in which the distance pieces are themselves strip metal annuli each lying between two adjacent scaling annuli and deformed so as to contact and hold apart said sealing annuli.

3. A seal as claimed in claim 1 in which the sealing annuli are of a metal strip of a thickness between 2 and 6 thousandths of an inch.

4, In apparatus comprising a rotor and a stator, in combination; a labyrinth seal carried by the stator and comprising a stack of annuli of thin metal strip having circular peripheral sealing edges, a plurality of distance pieces Iformed separately from and interleaved with said annuli to space the latter axially apart and strengthen them, said distance pieces being of less radial depth than said annuli to leave said peripheral sealing edges clear, and at least one relatively sharp ri-b carried by the rotor and arranged in substantial sealing relationship with said annuli, said rib being capable of cutting its own path in the annuli if rubbing therebetween occurs.

5. A seal `as claimed in claim 4 in which the sealing annuli are of a softer metal than that of the rib on the rotor.

6, A seal as claimed in claim 4 in which the sealing annuli are of a metal having a lower melting point than that of the 1ib on the rotor.

7. In apparatus comprising a rotor member and a stator member, in combination; a labyrinth seal carried by one of said members and comprising a channel-shaped ring, a stack of annuli of thin metal strip mounted therein, said annuli having cincular peripheral sealing edges, a plurality of independent distance pieces interleaved with said annuli to space the latter axially apart and strengthen them, said distance pieces being of less radial depth than said annuli to leave said peripheral sealing edges clear, and at least one n'b carried by the other of said members and arranged in substantial sealing relationship with said annuli, Vsaid rib being harder than said annuli for cutting its own path in the annuli if rubbing therebetween occurs.

8. A seal as claimed in claim 7 in which the sealing annuli are bent to form anges which abut laterally against andare integrally fixed to the bottom of the ring channel.

9. A seal as claimed in claim 7 in which the ring is mounted in the 'stator and there are means for applying cooling fluid to the ibase of the 4ring on the opposite side to the stack of annuli so as to cool the latter.

References Cited in the tile of this patent UNITED STATES PATENTS 580,049 Heim et a1. Apr. 6, 1897 1,190,500 Allen July 11, 1916 1,322,056 Roehl Nov. 18, 1919 1,686,937 Six Oct. 9, 1928 1,689,735 Losel Oct. 30, 1928 2,058,993 Keller Oct. 27, 1936 2,458,988 Gayer Jan. 11, 1949 2,963,307 Bobo Dec. 6, 1960 FOREIGN PATENTS 1,145,388 France May 6, 1957 793,886 Great Britain Apr. 23, 1958 407,012 France Dec. 20, 1909 

1. IN APPARATUS COMPRISING A ROTOR MEMBER AND A STATOR MEMBER, IN COMBINATION; A LABYRINTH SEAL AND A CONFRONTING RIB ONE WITHIN THE OTHER, SAID SEAL BEING CARRIED BY ONE OF SAID MEMBERS AND COMPRISING A STACK OF THIN STRIP METAL ANNULI HAVING CIRCULAR PERIPHERAL EDGES, A PLURALITY OF DISTANCE PIECES FORMED SEPARATELY FROM AND INTERLEAVED WITH SAID ANNULI TO SPACE THE LATTER AXIALLY APART AND STRENGTHEN THEM, SAID DISTANCE PIECES BEING OF LESS RADIAL DEPTH THAN SAID ANNULI TO LEAVE SAID PERIPHERAL SEALING EDGES CLEAR, AND AT LEAST ONE RELATIVELY SHARP CONTINUOUS RIB CARRIED BY THE OTHER OF SAID MEMBERS AND ARRANGED IN SUBSTANTIAL SEALING RELATIONSHIP WITH SAID ANNULI, SAID RIB BEING SIZED TO CUT ITS OWN PATH IN THE ANNULI IF RUBBING THEREBETWEEN OCCURS. 